1. Field of the Invention
The embodiments discussed herein are directed to a technology for determining the type of a vehicle.
2. Description of the Related Art
A system has been used in vehicle control tasks, etc. that analyzes an image of a vehicle captured by an image capture device installed on the road to determine the type of the vehicle. Typically, a known system analyzes a license plate portion in an image to determine the vehicle type. For example, Japanese Patent Application Laid-open No. 2003-331384 discloses such a system that determines the vehicle type by using not only the license plate number on the license plate but also the color of the license plate and others
In the license plate analysis, however, the vehicle type cannot be accurately determined when, for example, the license plate is dirty. Thus, if it is required to accurately determine the vehicle type under various conditions, a plurality of measures are combined to determine the vehicle type. For example, Japanese Patent Application Laid-open No. 2003-331384 discloses such a conventional technology for determining the vehicle type without depending on analysis of the license plate portion.
In this conventional technology, a hood portion and a windshield portion of a vehicle in an image are identified according to a predetermined rule and, based on the width and height of these portions, the type of the vehicle is determined as a standard-sized vehicle or a large-sized vehicle.
However, since the vehicle type is determined by the heights of the hood portion and the windshield portion and others, the vehicle type may be erroneously determined depending on the combination of the shape of the vehicle and the angle of an image capture device installed on the road.
In general, the height of the hood portion of a standard-sized vehicle in an image is lower as the image capture device is arranged at an angle closer to the horizontal and is higher as the angle is closer to the vertical. Therefore, depending on the angle of the image capture device, an image of the hood portion of a standard-sized vehicle of a specific type is captured with its height being approximately equal to the height of the hood portion of a large-sized vehicle, and the standard-sized vehicle may be erroneously determined as a large-sized vehicle. Since vehicles have its own characteristic shape depending on the type, it is difficult to completely prevent such an erroneous determination even if the angle of the image capture device is adjusted.